Debian 9 change default UI from built in Gnome to LXDE
 

sometime back I set a unit to not boot into GUI by issuing cmd
systemctl set-default multi-user.target
And I want to keep this, but occasionally I do want to use a GUI and do so by cmd startx.
But I struggle with the built in Gnome and would prefer to use LXDE.
I've installed the LXDE via apt, but I haven't found how to make it the default GUI, so that when I startx it starts LXDE.
Any pointers?
K.

I would expect and /usr/share/xsessions/x-window-manager to provide the solution.is probably showing /usr/bin/gnome currently, and needs a switch to /usr/bin/lxde. Here it shows

in Debian 9 Stretch there is no /usr/share/xsessions/x-window-manager

/usr/share/xsessions only has .desktop files for gnome-classix, gnome, lightdm, LXDE and openbox

in Debian 9 Stretch the following
update-alternatives -get-selections
needs to be
update-alternatives --get-selections

it shows
x-session-manager auto /usr/bin/gnome-session
x-window-manager auto /usr/bin/openbox

- - -

separately I found /usr/bin/startlxde
but it responds

** Message:main.vala:102: session is LXDE
** Message:main.vala:103: DE is LXDE

(lxsession:6041): Gtk-WARNING ** cannot open display

Hi. ¿Have you tried gdm3 o gdmflexiserve? It start gdm (xserver manager) and then you can select your window manager.
Have a nice day.

As root:
But I struggle with the built in Gnome and would prefer to use LXDE.

Now, when you reboot, no display manager is running

to re-enable it.

Create a file in $HOME, .xinitrc

This will run LXDE every time you issue the startx command.

Alternatively, if you want to switch for one session only:
replace startlxde with the session you wish to use for that session. IIRC it mus be a fulll, absolute path.